RE: audio oscillator (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 29 Jun 2007 19:20:08 -0400
From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: audio oscillator (fwd)

Ahh - I was thinking of the circuit with two op amps, but I think the
2nd one actually was a comparator to flip the input drive to the 1st
integrator on alternate half-cycles.  I don't think I've ever seen a
double-integrator circuit, and you'd need a 3rd amp/comparator to flip
the polarity.

Thanks, Gary Lau
MA, USA

> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Friday, June 29, 2007 3:06 PM
> To: tesla@xxxxxxxxxx
> Subject: RE: audio oscillator (fwd)
> 
> 
> ---------- Forwarded message ----------
> Date: Fri, 29 Jun 2007 11:33:55 -0700
> From: Jim Lux <jimlux@xxxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: RE: audio oscillator (fwd)
> 
> At 07:34 AM 6/29/2007, you wrote:
> 
> >---------- Forwarded message ----------
> >Date: Fri, 29 Jun 2007 10:34:27 -0400
> >From: "Lau, Gary" <Gary.Lau@xxxxxx>
> >To: Tesla list <tesla@xxxxxxxxxx>
> >Subject: RE: audio oscillator (fwd)
> >
> >Wouldn't op-amp integrators result in triangle-waves?  Making sine
waves
> >is a bit trickier.
> 
> double integration gets pretty close, parabolic instead of linear.
> 
> The Exar part actually has a chain of RCs that gets very close to
> sinusoid (sub 1% THD, as I recall), and some of the HP function
> generators do the same.
> 
> Kind of depends what tuning range, etc. you need, which approach to
> use.  It's hard to beat a nice Wien bridge for low distortion, but it
> doesn't have wide tuning range.
> 
> 
>